Method of apparatus for forming an object by means of additive manufacturing

Abstract

A method of and an apparatus (1,29) for forming an object by means of additive manufacturing, the method comprising consecutively providing a plurality of layers (9) of building material (5, 6), and selectively curing one or more pixels (47) of each of the layers (9) during printing thereof. The method comprises a step of providing a first layer (9) of a first building material (5) onto a support surface (4, 30) or a preceding layer (9), and selectively exposing, in accordance with layer data, one or more pixels (47) in the first layer (9) to a dose of radiation (45, 45′). It further comprises the identifying, based on the layer data, of one or more contour pixels (47) in the first layer (9) that coincide with a contour of a featured region of a subsequent second layer (9), wherein the featured region of the second layer (9) is to be provided using a second building material (6) different from the first building material (5). The method also comprises increasing, prior to said selectively exposing, a radiation dose (45′) for the identified contour pixels (47). The step of selectively exposing includes exposing the one or more contour pixels (47) using the increased radiation dose (45′).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application is a U.S. National Phase of PCT International Application No. PCT / NL2019 / 050209, filed Apr. 9, 2019, which claims priority to European Application No. 18166297.4 filed Apr. 9, 2018, which are both expressly incorporated by reference in their entireties, including any references contained therein.FIELD OF THE INVENTION[0002]The present document is directed at a method of forming an object by means of additive manufacturing, the method comprising consecutively providing a plurality of layers of building material, and selectively curing one or more pixels of each of the layers during printing thereof, the method comprising: providing a first layer of a first building material onto a support surface or a preceding layer; and selectively exposing, in accordance with layer data, one or more pixels in the first layer to a dose of radiation.[0003]The document is further directed at an apparatus for forming an object by mea...

AI Technical Summary

Benefits of technology

The present invention is an additive manufacturing method and apparatus that allows for the quick and accurate formation of multi-material objects. The invention is based on the premise that the level of curing (how well the pixels are cured) of pixels can be increased by using an increased radiation dose. This will reduce or even remove the oxygen inhibition layer, which causes the problem of spreading the second building material across the surface of the layer underneath. The one or more contour pixels in the first layer are determined and exposed with the increased radiation dose to increase their level of curing or even fully cure them. This will allow the featured region to be accurately printed using the second building material. The method also includes identifying fill-in pixels that coincide with the featured region in the second layer and exposing them with the increased radiation dose to improve their wetting characteristics and prevent the second building material from spreading beyond them. The thickness of the oxygen inhibition layer at the location of the at least one pixel is measured to determine the radiation dose needed for the desired level of curing.

Problems solved by technology

Although the same effect could potentially also be achieved by fully curing of the whole surface of the first layer, to completely get rid of the oxygen inhibition layer; the inventors have realized that this is usually not desired either as it gives rise to other disadvantages.

Fully curing of the first building material in those areas where, in the consecutive second layer, a next layer of first building material is to be applied is experienced to result in poorer adhesion.

Hence in those areas (i.e. the areas outside the featured region), adhesion will be poor which in turn results in a weak spot: the layer may peel off or tear, or may be less shock proof.

Hence, fully curing of the whole first layer results in an integrity problem.

Moreover, the full curing may further result in a color difference, which is typically not desired.

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